Bypass switch and vacuum interrupter



8- 11970 c. w. SCHOENDUBE 3,524,033

BY PASS SWITCH AND VACUUM INTERRUPTER Filed April 5, 1968 3 Sheets-Sheetl 7""? r" g; 16 l2; l I. .4 non [2' i E l i 15 E 19 20 f 2 i i E 14'. i6 a i E v 1' E 22 l i 3 '--z4 I i l Aug. 11, 1970 v -c. w. SCHOENDUBEBYPASS SWITCH AND VACUUM IN'IERRUPTER 3 Sheets-Sheet. 2

Filed April 3, 1968 Aug. 11, 1970 c. w. SCHQENDUBE 3 BYPASS SWITCH ANDVACUUM INTERRUPTER 3 Sheets-Sheet 3 Filed April 5, 1968 (Zar/es W52606120256 United States Patent 3,524,033 BYPASS SWITCH AND VACUUMINTERRUPTER Charles W. Sclroendube, Lee, Mass., assignor to GeneralElectric Company, a corporation of New York Filed Apr. 3, 1968, Ser. No.718,597 Int. Cl. H01h 33/66, 3/42 US. Cl. 200-144 8 Claims ABSTRACT OFTHE DISCLOSURE The application discloses a combined bypass switch andvacuum interrupter to be used in connection with a tap-changingmechanism for a transformer or regulator. A rotatable bypass switchingcam disc alternately makes and breaks a pair of contacts which areconnected to both the vacuum interrupter and the tap-changing contacts.The bypass switching cam disc is also electrically connected to theload. Two concentric cylindrical cams are mounted with the cam disc on ahollow shaft. A yoke is provided and is imparted with a reciprocatingmotion by two cam followers which are connected to the yoke and operatedby the cylindrical cams. The yoke is adapted to transmit thereciprocating motion to a push-pull shaft which is positionedconcentrically within the hollow shaft and is connected to a buttcontact within the vacuum interrupter. All the cams are adapted andarranged to synchronize the bypass switching with the vacuum interrupterswitch so as to provide a proper sequence of operation for safelychanging tap connections on a transformer.

BACKGROUND OF THE INVENTION The invention relates to switchingmechanisms and, more specifically, to a mechanism which properlysynchronizes the operation of two bypass switches with a vacuuminterrupter switch shunted across them, which These costly mechanismshave proved impractical as they include large, motor-driven, bypass andoil-break interrupter switches switches which are linked to a tapchanger mechanism by a dispersed configuration of members which arecomplexly arranged over a large insulating board. Furthermore, with eachoperation of each oilbreak interrupter switch, carbon particles areformed in the oil surrounding the switch mechanism. This results in thedegradation of the dielectric strength of the oil which, in turn,requires that greater strike and creep insulation distances, and alsointerrupter movement, be provided between the live parts of themechanism to insure safe operation. For these reasons the existingmechanisms have had to be unduly large, unnecessarily complicated andundesirably ineflicient.

If a smaller vacuum type interrupter switch were to be used in place ofthe oil-break interrupter, however, the carbon-forming arc would beisolated from the oil and a more compact and simplified unit would bepossible. Likewise, a more efiicient mechanism could be provided as theimproved interrupting features of a vacuum switch would provide agreater number of interruptions than presently obtainable with existingoil-break interrupters from the same volume of contact material.Further, less contact gap opening is required with vacuum switches whichreduces the power drive requirement of the mechanism.

Accordingly, it is one object of this invention to provide a combinedbypass and interrupter switch mechanism which will not cause a reductionin the dielectric strength of a surrounding oil.

It is another object of this invention to provide a combined bypass andinterrupter switch mechanism which is compact and simple.

It is a further object of this invention to provide a combined bypassand interrupter switch mechanism which is inexpensive and adaptable foruse with existing transformer tap selector mechanisms.

A. still further object of this invention is to provide a combinedbypass and interrupter using a vacuum switch to increase the efiiciencyand reduce power drive requirements.

SUMMARY OF INVENTION In carrying out the invention in the preferredform, a combined bypass and vacuum interrupter switch mechanism isprovided having a switching cam disc for operating two bypass switches.Two concentric cylindrical cams are provided for operating the vacuuminterrupter in proper synchronization with the bypass switches. Theswitching cam disc and the concentric cylindrical cams are mounted on ahollow shaft which has a push-pull shaft positioned concentricallytherein. As the hollow shaft is rotated, the disc operates the bypassswitches and the two cylindrical cams operate the vacuum interrupterthrough a yoke member which transmits a reciprocating motion to thepush-pull shaft which, in turn, operates the vacuum interrupter.

BRIEF DESCRIPTION OF DRAWINGS The specification concludes with claimswhich partic ularly point out and distinctly claim the invention whichissought to be protected and a preferred embodiment is disclosed in thefollowing detailed description in connection with the accompanyingdrawings in which:

FIG. 1 is a schematic diagram of a tap changing circuit to which theswitching function of the invention is to be applied;

FIG. 2 is a perspective view of a vacuum interrupter and bypass switchaccording to the preferred embodiment of this invention; 1

FIG. 3 is a plan view of the driving gear and cam portion of thepreferred embodiment of the invention;

FIG. 4 is a front view of the preferred form of bypass switching cam ofthe invention;

FIG. 5 is a side view of one of the bypass switch contacts;

FIG. 6 is a partial sectional view showing the relation of onecylindrical cam and the roller cam follower according to the preferredembodiment; and

FIG. 7 is a partial sectional view showing the relation of the othercylindrical cam and the roller cam follower according to the preferredembodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to thedrawings in which like numerals are used to indicate like partsthroughout the various views thereof, a schematic diagram of thecircuitry to which the preferred embodiment of this invention is to beapplied is shown in FIG. 1 as two tap selector contacts 12 and 14 whichare connected through reactor coils 16 and bypass switch contacts 12'and 14 to a load contact 18. A vacuum interrupter switch 20- is shuntedacross the parallel circuit formed by the aforementioned connections andit is to the proper synchronizing of the operation of the vacuuminterrupter 20 with the opening and closing of the bypass switchcontacts 12' and 14 that the function of the invention is specificallydirected. The portion of the circuit which is to be directely affectedby the subject matter of this invention is shown diagrammatically asblock 22.

When a transformer or regulator tap changer mechanism, shown as block24, causes contact 12 to move from stationary contact 26 towardstationary contact 28, it is necessary to open contacts 12 whereby,one-half the load current is shunted through vacuum interrupter 20.Interrupter 20 must then be opened to cause zero current through contact12 and full load current through the connection between contact 14,contacts 14 and load contact 18. As contact 12 physically reachesstationary contact 28, it is necessary to reclose vacuum interrupter 20so as to divide the load current through tap selector contacts 12 and 14which are now both on stationary contact 28. Bypass contacts 12 must nowbe closed to relieve vacuum switch 20 of continuous current carryingduty.

Referring now to FIG. 2, the preferred embodiment of the bypass andvacuum interrupter of this invention is shown as including the bypassswitch contacts 12 and 14 and vacuum interrupter switch 20. A switchingdisc 30' is mounted on a hollow shaft 32 and, when rotated, disc 30properly opens contacts 12' or 14', depending on the direction oftraverse applied to tap selector contacts 12 and 14. The preferred shapeof disc 30 is clearly shown in FIG. 4. As shown in FIG. 4 disc 30 has ahub 30- rmounted on and secured to hollow shaft 32. Switching disc 30rotates 180 per tap change sequence, opening contacts 12 and 14alternately. A smaller concentric shaft 34 is positioned within hollowshaft 32 and is directly connected to a butt contact 36, which is housedwithin the overall vacuum interrupter 20 along with a mating buttcontact 38. By a driving means described later in the disclosure, areciprocating motion is transmitted to shaft 34 in such a manner thatbutt contact 36 is separated from butt contact 38 immediately aftereither contacts 12' or 14' are opened. The load current contact 18 alsoengages switching disc 30 and is so adapted as to provide proper andcontinuous electrical contact regardless of the angular position of disc30. As shown in FIG. 2, the parallel circuit of FIG. 1 is structurallyprovided by connecting tap selector contacts 12 and 14 through mutuallycoupled induction coils 16 and contacts 12' and 14 to load contact 18 bymeans of disc 30. Vacuum switch 20 is shunted across the circuit byconnecting contacts 14' to the butt contact 38 and contacts 12 to thebutt contact 36, which is mounted on one end of the rod 34.

As shown in FIG. 2, the driving portion of the preferred embodimentincludes a drive pinion 40 and a large driven gear 42. Pinion 40 isdriven from a motor (not shown) through a gear train (not shown) which,as will be understood, also operates the tap changer mechanism. Gear 42is directly and concentrically secured to a cylindrical cam 44. A hub 46is formed on cylindrical cam 44, which hub 46 fits within one end of thehollow shaft 32. Cylindrical cam 44 is formed with two gradual rise anddropoff projections 50 with which rollers 52 cooperate as cam followers.The rollers 52 are mounted on a reciprocating yoke 54 and cause the yoketo move to the right as the rollers 52 are forced to ride up the gradualcam projections 50.

FIG. 3 shows the driving portion of the invention as it is properlysecured to a panel 56 by means of a large hollow and flanged stud 58over which the hub 46 is rotatably mounted. As previously explained,hollow shaft 32 is rotatably mounted on hub 46. A hammer member 60 isattached to the inside of the yoke 54 and is adapted to engage an anvilmember 62 which is secured to the push-pull shaft 34. A helical spring64 is disposed between the yoke 54 and the mounting panel 56 so as toexert a force slightly greater than 30 pounds to the yoke 54 in biasingit to the left. Stop means 66 which mount roller cam followers 52 on theyoke 54 on the opposite side of panel 56 from spring 64 limit the stroketravel of yoke 54 as it moves to the left. The limit to the travel ofyoke 54 as it is moved to the right is determined by the projections 50on cam 44. The yoke 54 is slidably mounted in bearings '68 which areformed in the panel 56. As will be apparent, this mounting prevents therotation of yoke 54 when roller cam followers 52 engage the camprojections 50. The hollow stud 58 provides the supporting means for thehub 46 and hollow shaft 32 as previously described.

As is apparent from FIGS. 2 and 3, when cam 44 is rotated, roller camfollowers 52 will engage the leading edge of cam projections 50. Furtherrotation of cam 44 causes cam followers to ride up the gradual slope ofcam projections 50, moving yoke 54 and hammer member 60 to the right,compressing spring 64. This will relieve the spring pressure on shaft 34permitting the vecuum contacts 36 and 38 to be closed by atmosphericpressure. In the preferred embodiment shown, the spring 64 must apply abias force to the shaft 34 of a magnitude greater than 30 pounds whenhammer 60 engages anvil 62 in order to permit separation of the vacuumenclosed contacts 36 and 38. This requirement is due to atmosphericpressure acting on some two square inches of bellows area 70, which arelocated within the vacuum switch 20 and within which the contact 36 ismounted.

To obtain proper interrupting action at low erosion rates, it becomesnecessary to open the vacuum contacts 36 and 38 rapidly. However, toinsure long bellows life and a bounce-free closing action, it isnecessary to close these contacts slowly. Since it is desirable to beable to tap select in both directions, it is important that this quickopening and slow closing action be provided regardless of the directionof rotation of cylindrical cam 44. It is for this reason that an innercylindrical cam 72, which is concentrically attached to cam 44, isprovided. The inner cam 72 is provided with a hub 73 which fits overhollow shaft 32 and is secured thereto by a set screw 75. Cam 44 isprovided with two pins 74, which couple with two arcuate slots 76 formedin cam 72. The inner cam 72 is also provided with two cam projections 78which correspond to the projection 50, except that the projections 78have a sharp drop-off profile and projections 50 have a gradualdrop-off. This can be clearly seen in FIGS. 6 and 7.

In operation, if power is applied by the drive pinion 40 so as to rotatethe gear 42 in a clockwise direction, a complete operating sequenceoccurs. The large driven gear 42 rotates until the coupling pins 74bottom against the leading edges of the slots 76 formed in the innercylindrical cam 72. As previously mentioned, hollow shaft 32 isrotatably mounted on hub 46 of cam 44 while both cam 72 and switch cam30 are fixed to hollow shaft 32. The sliding friction provided by thecontacts 12, 14' and the contact 18 on switch cam 30 prevents anyfriction drive between the inner cam 72 and the outer cam 44. As can beseen from FIG. 5, switch contacts 12' are forced against switch cam 30by spring 13, providing the desired friction. The width of the slot 76is such as to have the trailing gradual rise portion of the outer camprojection 50 of cam 44 completely overlapped by the trailing portion ofthe sharp rise projection 78 of cam 72 when the pins 74 bottom. A sharpdrop-out point is thus formed for the roller cam followers 52, whichsharp drop-out provides the means for satisfying the requirement forquickly opening the vacuum switch contacts 36 and 38.

Before this drop-out point is reached, however, the switching disc 30will be rotated the required number of degrees needed to disengage thecontacts 12 from the disc 30. Thus, with 12' open, the rollers 52drop-off sharply from the inner cam projection 78 as shown in FIG. 7 andthe yoke 54 moves to the left causing the hammer 60 to strike the anvil62 which is connected to the vacuum switch push-pull rod 34. The vacuumswitch butt contacts 36 and 38 are thereby rapidly opened. The cam yoke54 continues to move to the left until the stop means 66 contact themounting panel 56 which relieves the cams of any unnecessary impactforces. The anvil 62 and pull rod 34 continue to move to the left afterimpact until they are stopped by the atmospheric 30-pound pull forceexerted on butt contact 36 by the vacuum bellows 70 of switch 20. Themotion of the rod 34 is then reversed by the atmospheric pressure untila cushioned catch is made by the hammer 60 which is biased to the leftby the discharge spring 64.

After the vacuum switch 20 is opened, the tap selector contact 12 may bemoved to stationary contact 28. A conventional tap selector (not shown)is geared off of the drive pinion 40 in such a manner as to besynchronized with the operation of the present invention. After furtherrotation of the inner cam 72 and outer cam 44, a gradual rise slope ofthe outer cam projection 50 is encountered by the rollers 52, as shownin FIG. 6. As the rollers are driven to the closed position shown inFIG. 3, the yoke 54 slowly moves to the right, carrying with it thehammer 60, which in turn permits contacts 36 and 38 to slowly closeunder the 30-pound atmospheric force. In this manner the secondrequirement of slowly closing contacts 36 and 38 has been satisfied.

A complete sequence of operation has been described with such a sequenceoccurring no matter which direction the mechanism is driven. To minimizeovershoot of the anvil 62, a dashpot dampening mechanism (not shown anddescribed a particular embodiment of the into the end of the stroke ofyoke 54. A set of electrical control contacts (also not shown) which areto be operated off of the tubular shaft 32, may be provided to insurethat the drive power is removed and rotation stopped when the rollers 52rest at approximately the central portion of the inner cam projections78 after every 180 of rotation of the cylindrical cams 44 and 72 fromthis position.

It should be understood that, while there has been shown and described aparticular embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madewithout departing from the spirit and scope of the invention.

For example, if desired, cam 44 and gear 42 could be a single member,with cam projections 50 and pins 74 directly mounted on gear 42. It willbe apparent that these and other modifications may be made within thescope of the invention as defined in the claims appended hereto.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A bypass switch and vacuum interrupter mechanism comprising, incombination:

(a) a pair of bypass switches,

(1) a switching cam disc opening and closing said bypass switches,

(b) a hollow, rotatable shaft,

(1) said cam disc secured to said hollow shaft,

(c) a second shaft,

(1) said second shaft concentrically mounted within said hollow shaft,

(d) a vacuum interrupter electrically connected between said bypassswitches,

(1) one contact of said vacuum interrupter connected to one end of saidsecond shaft,

(e) a cylindrical cam,

(1) said cylindrical cam having a pair of cam projections,

(2) means for rotatably mounting said cylindrical cam,

(3) said cylindrical cam including means to rotatably mount said hollowshaft,

(f) a yoke member,

(1) said yoke member slidably mounted with re spect to said cylindricalcam,

(2) a pair of cam followers on said yoke member riding on saidcylindrical cam,

(3) means interconnecting said yoke and said second shaft for reciprocalmovement of said second shaft,

(g) means for driving said cylindrical cam, and

(h) lost motion means interconnecting said cylindrical cam and saidhollow shaft for rotation of said hollow shaft and said switching camdisc.

2. A bypass switch and vacuum interrupter mechanism as set forth inclaim 1 in which said yoke is provided with a sliding connection to theother end of said second shaft for moving said second shaft to open saidvacuum interrupter, spring biasing means to bias said yoke in positionto maintain said vacuum interrupter open, and said cam followerscooperating with said cam projections to compress said spring and closesaid vacuum interrupter.

3. A bypass switch and vacuum interrupter as set forth in claim 1, saiddriving means include a gear fixed to said cylindrical cam and said lostmotion connection includes a second cylindrical cam fixed to said hollowshaft and connected to said cylindrical cam through pins on saidcylindrical cam and slots in said second cylindrical cam.

4. The bypass switch and vacuum interrupter mechanism as set forth inclaim 1 in which pins project from one face of said cylindrical cam; asecond cylindrical cam; arcuate slots formed in said second cylindricalcam; said second cylindrical cam fixed on said hollow shaft with saidpins of said first cam extending through said slots of said second camforming a lost motion connectio, cam projections formed on said secondcam; each said second cam projection having a sharp rise and a sharpdrop-off; said first and second cam projections being so positioned andsaid second cam slots being of such a width that, as said second cam isdriven by said first cam; said first cam projections and said second camprojections form a single composite cam projection with a gradual riseleading edge and a sharp drop-off trailing edge, regardless of thedirection of rotation.

5. A bypass switch and vacuum interrupter mechanism comprising, incombination: two bypass switches; a Switching cam disc for operatingsaid bypass switches; a first shaft for mounting said switching camdisc; a load current switch; said load current switch adapted to engagesaid switching cam disc regardless of the angular position of said disc;a vacuum switch interrupter connected between said bypass switches; asecond shaft; said vacuum interrupter switch connected to a first end ofsaid second shaft; said second shaft adapted for applying a push-pulloperating force to said vacuum interrupter; a cylindrical cam mountedrotatably with respect to said first shaft for operating said vacuumswitch through a mechanical linkage with said second shaft; a yokemember; said yoke member provided with cam followers for riding on saidcylindrical cam; a hammer member mounted on said yoke; an anvil membermounted on a second end of said second shaft; said hammer and said anvildisposed in driving relationship so that a reciprocating motion may betransmitted between said second shaft and said yoke; a panel formounting said shafts and said yoke; a spring disposed between said paneland said yoke for biasing said vacuum interrupter to the open positionthrough a mechanical linkage between said yoke and said second shaft;means for driving said first shaft; said driving means adapted tosynchronize said bypass switches and said vacuum interrupter with alinked electrical contact changer; cam projections formed on saidcylindrical cam; said cam projections so formed as to cause the vacuuminterrupter to open immediately after one said bypass switch is openedand to close immediately before said bypass switch is closed.

6. A bypass switch and vacuum interrupter as claimed in claim 5 in whichsaid first shaft is hollow and said second shaft is concentricallymounted in said first shaft.

7. A bypass switch and vacuum interrupter as claimed in claim 5 in whicha lost motion connection is provided between said cylindrical cam andsaid bypass switching cam disc, said lost motion connection comprising asecond cylindrical cam fixed to said first shaft, said secondcylindrical cam having a pair of arcuate slots, pins on said firstcylindrical cam and extending through said arcuate slots.

8. A bypass switch and vacuum interrupter as claimed in claim 7 in whichsaid second cam has cam projections provided with sharp rise anddrop-off edges, said first cylindrical am having gradual rise anddrop-off edges on said cam projections and said arcuate slots sopositioned that as said second cylindrical cam is driven by said firstcam said first cam projections and said second cam projections formsingle composite cam projections with a gradual rise and a sharpdrop-01f, regardless of direction of rotation.

References Cited UNITED STATES PATENTS 3,206,580 9/1965 McCarty.3,404,247 10/ 1968 Glassanos. 3,467,800 9/1969 Barr.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,524,033 Dated August 11 1970 Charles W. Schoendube Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 2, line 71, "directely" should read directly Column 4, line 12,"vecuum" should read vacuum Column 5 line 24, cancel entire line andinsert shown) may be provided so as to engage slightly prior Column 6,line 25 "tio" should read tion Column 7, line 6 "am" should read camSigned and sealed this 24th day of November 1970 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents FORM PO-IOSO (10-69) a u s covnuunn rmn'rmcQH'ICE: uu o-su-su

